U.S. patent application number 10/205882 was filed with the patent office on 2003-02-20 for differential transmission line for high bandwidth signals.
Invention is credited to Tzeng, Liang D..
Application Number | 20030034854 10/205882 |
Document ID | / |
Family ID | 27394862 |
Filed Date | 2003-02-20 |
United States Patent
Application |
20030034854 |
Kind Code |
A1 |
Tzeng, Liang D. |
February 20, 2003 |
Differential transmission line for high bandwidth signals
Abstract
In one aspect, the invention relates to a waveguide structure
for differential transmission lines. The waveguide structure
includes a first ground structure, a first signal line, a second
ground structure, a second signal line, a third ground structure.
The first signal line is typically positioned adjacent and
substantially parallel to the first ground structure. The second
ground structure has a first separation distance from the first
ground structure and is typically positioned adjacent and
substantially parallel to the first signal line. The first signal
line is typically positioned between both the first and second
ground structures. The second signal line typically has a second
separation distance from the first signal line and is positioned
adjacent and substantially parallel to the second ground structure.
The second ground structure is typically positioned between both
the first and second signal lines. The third ground structure
typically has a third separation distance from the second ground
structure and is positioned adjacent and substantially parallel to
the second signal line. The second signal line is typically
positioned between both the second and third ground structures.
Inventors: |
Tzeng, Liang D.; (Belle
Mead, NJ) |
Correspondence
Address: |
TESTA, HURWITZ & THIBEAULT, LLP
HIGH STREET TOWER
125 HIGH STREET
BOSTON
MA
02110
US
|
Family ID: |
27394862 |
Appl. No.: |
10/205882 |
Filed: |
July 26, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60312373 |
Aug 16, 2001 |
|
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60325875 |
Sep 28, 2001 |
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Current U.S.
Class: |
333/5 ;
333/238 |
Current CPC
Class: |
H01P 3/003 20130101;
H05K 1/0219 20130101; H05K 2201/09236 20130101; H05K 2201/09336
20130101 |
Class at
Publication: |
333/5 ;
333/238 |
International
Class: |
H01P 003/04 |
Claims
What is claimed is:
1. A waveguide structure for differential transmission lines
comprising: a first ground structure; a first signal line
positioned adjacent and substantially parallel to the first ground
structure; a second ground structure, having a first separation
distance from the first ground structure, positioned adjacent and
substantially parallel to the first signal line, wherein the first
signal line is positioned between both the first and second ground
structures; a second signal line, having a second separation
distance from the first signal line, positioned adjacent and
substantially parallel to the second ground structure, wherein the
second ground structure is positioned between both the first and
second signal lines; and a third ground structure, having a third
separation distance from the second ground structure, positioned
adjacent and substantially parallel to the second signal line,
wherein the second signal line is positioned between both the
second and third ground structures.
2. The waveguide structure of claim 1 wherein the first signal line
has a substantially constant width.
3. The waveguide structure of claim 1 wherein the first and second
signal lines have a substantially constant width.
4. The waveguide structure of claim 2 wherein the width of the
first signal line and the separation distances are sufficiently
sized to permit fabrication of a circuit element on the first
signal line.
5. The waveguide structure of claim 3 wherein the width of the
first and second signal lines and the separation distances are
sufficiently sized to permit fabrication of a circuit element on
the first signal line and second signal lines.
6. A differential transmission line system comprising: a first
communication device having at least five pin inputs; a second
communication device having at least five pin outputs; and a
differential signal line having at least ten contacts arranged in a
decoupled cofiguration, wherein the first and second communication
devices are connected to the differential signal line in a
differential decoupled configuration.
7. The differential transmission line system of claim 6 wherein the
differential signal line further comprises two signal lines and
three ground structures.
8. A waveguide structure for differential transmission lines
comprising: at least two signal lines; and a plurality of ground
structures, wherein each signal line is adjacent to two ground
structures.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefits of provisional U.S.
patent application Ser. No. 60/312.373 filed on Aug. 16, 2001 and
U.S. patent application Ser. No. 60/325,875 filed on Sep. 28, 2001
the disclosures of which are hereby incorporated herein by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention generally relates to the field of
signal propagation. In particular, the present invention relates to
a waveguide configuration for signal propagation in
telecommunication devices.
BACKGROUND OF THE INVENTION
[0003] Differences in voltage are central to the operation of
virtually all electrical circuits. Differential signaling relates
to a particular application of this general concept. Specifically,
two signals are sent from one device as outputs. These two signals
are received by a second device as inputs. The information
contained within the signals is derived from the differences in
voltage or current between them by the second device. This allows
various external noise signals to be subtracted out when the inputs
are processed. The differences in signals convey the information
rather than one signal evaluated with respect to a ground. When
transmitting at very high data rates, over long distances and
through noisy environments, single-ended transmission is often
inadequate. In these applications, differential data transmission
offers superior performance.
[0004] The primary disadvantages of differential signaling result
from the additional space, design complexity, and production costs
association with increasing the number of pins, traces and
tranceivers. These disadvanatges can limit the overall efficiency
and suitability for a differential signaling system in different
operating environments. Therefore a need exists for communication
devices and differential signaling systems that maintain the
advantages while reducing the inefficiencies associated with using
differential based signaling techniques.
SUMMARY OF THE INVENTION
[0005] In one aspect, the invention relates to a waveguide
structure for differential transmission lines including first,
second, and third ground structures (e.g., ground planes) and first
and second signal lines. The width of the first signal line and the
separation between the first signal line and each of the first and
second ground structures are sufficient to permit fabrication of a
circuit element on the first signal line in some embodiments. In
another aspect, the invention relates to providing complementary
decoupled differential transmission line connections between signal
transmission lines and optical-electronic receivers and
demultiplexing devices. In another aspect, the invention relates to
connecting communication devices with an electrical ground (G) and
signal (S) connections arranged in a G-S-G-S-G configuration.
[0006] In one aspect, the invention relates to a waveguide
structure for differential transmission lines. The waveguide
structure includes a first ground structure, a first signal line, a
second ground structure, a second signal line, a third ground
structure. The first signal line is typically positioned adjacent
and substantially parallel to the first ground structure. The
second ground structure has a first separation distance from the
first ground structure and is typically positioned adjacent and
substantially parallel to the first signal line. The first signal
line is typically positioned between both the first and second
ground structures. The second signal line typically has a second
separation distance from the first signal line and is positioned
adjacent and substantially parallel to the second ground structure.
The second ground structure is typically positioned between both
the first and second signal lines. The third ground structure
typically has a third separation distance from the second ground
structure and is positioned adjacent and substantially parallel to
the second signal line. The second signal line is typically
positioned between both the second and third ground structures.
[0007] In one embodiment, the first signal line has a substantially
constant width. The first and second signal lines have a
substantially constant width in another embodiment. In another
embodiment, the width of the first signal line and the separation
distances are sufficiently sized to permit fabrication of a circuit
element on the first signal line. In another embodiment, the width
of the first and second signal lines and the separation distances
are sufficiently sized to permit fabrication of a circuit element
on the first signal line and second signal lines.
[0008] In another aspect, the invention relates to a differential
transmission line system. The differential transmission line system
includes a first communication device, a second communicator
device, and a differential signal line. The first communication
device typically has at least five pin inputs. The second
communication device typically has at least five pin outputs. The
differential signal line typically has at least ten contacts
arranged in a decoupled configuration. The first and second
communication devices are typically connected to the differential
signal line in a differential decoupled configuration. In one
embodiment, the differential transmission line system further
comprises two signal lines and three ground structures.
[0009] In another aspect, the invention relates to a waveguide
structure for differential transmission lines. The waveguide
structure typically includes at least two signal lines and a
plurality of ground structures, wherein each signal line is
adjacent to two ground structures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic cross-sectional view of a transmission
line as known in the prior art;
[0011] FIG. 2 is a schematic cross-sectional view of another
transmission line as known in the prior art;
[0012] FIG. 3 is a schematic cross-sectional view of a transmission
line according to an illustrative embodiment of the invention;
and
[0013] FIG. 4 is a view of FIG. 3 with an incorporated electrical
element according to an illustrative embodiment of the
invention.
DETAILED DESCRIPTION
[0014] FIG. 1 illustrates a known single-ended coplanar
ground-signal-ground (GSG) type transmission line 100 (e.g.,
waveguide on a circuit board). The impedance of the transmission
line is dependent on the material composition and thickness of the
substrate 110, the width 115 of the signal line 120 and the
separation 125 between the signal line 120 and the ground plane
130. In order for a high bandwidth signal to propagate without
distortion, a transmission line that accurately presents a design
impedance (e.g., 50 .OMEGA.) to the signal is required.
[0015] FIG. 2 illustrates a differential transmission line having a
ground-signal-signal-ground (GSSG) configuration 200 as is known in
the prior art. The signal lines 210 support a differential signal
mode. To achieve a predetermined impedance, the width 215 of the
signal lines 210 and the separation 220 between the signal lines
210 must be accurately controlled. The properties of the substrate
225 can also be modified to affect the impedance. Typically the
separation 220 is small (e.g., on the order of 0.005 inches)
compared to the width 215 of the signal lines (e.g., typically in
the range of 0.015 to 0.020 inches). The separated signal lines 210
are shown in between two ground structures 230.
[0016] Most receiver module packages on the market today have an
output signal strip line configuration which relies on the
differential signals being coupled as shown in FIG. 2. This pinout
arrangement is referred to as the G-S-S-G configuration or
"coupled." For most applications, these same receiver module
packages with the G-S-S-G pinout will require the optical receiver
module to be interfaced to a demultiplexing integrated circuit to
remove the various multiplexed signals. Demultiplexing integrated
circuits typically have input signal pinouts with a G-S-G-S-G
configuration, which is also defined as a differential decoupled
configuration. In one aspect the invention relates to designing
various optical devices, such as optoelectronic receivers, with a
signal leads in a G-S-G-S-G configuration to more easily interface
with other communication devices such as a demultiplexing
integrated circuit based devices.
[0017] In some applications, circuit components are required along
the transmission lines. For example, AC coupling requires inclusion
of a capacitor on each signal line. Still referring to FIG. 2, in
many instances, the small separation 220 between the signal lines
for a GSSG configuration prohibits integration of the capacitors
into the waveguide structures, especially if the application
requires large capacitance values.
[0018] FIG. 3 illustrates a differential transmission line having a
ground-signal-ground-signal-ground (GSGSG) configuration 300. This
GSGSG configuration of signal lines and ground structures is also
referred to as a differential decoupled configuration. The
separation 305 between each signal line 310 and the adjacent ground
plane 315 is substantially greater than the separation 220 between
the signal lines 210 of FIG. 2 in this illustrative embodiment.
[0019] Circuit elements, such as capacitors 405, can be integrated
into the waveguide structure 300' as illustrated in FIG. 4. The
substrate material 312 can be modified to accommodate additional
circuit elements in various embodiments. Additional circuit
elements include resistors, inductors, diodes, tansistors,
integrated circuit devices, and any other suitable electronic
device. Referring to FIG. 4, if the circuit element is too large to
be accommodated by the nominal width 320 and separations 305' of
the transmission lines, the structure of the transmission line can
be arranged, for example, by expanding the line width 320' find
separation 305' to accept the circuit element and achieve the
desired impedance. The line widths and separations in all aspects
of the invention can be varied based on the requirements of a
giving signal transmission set up.
[0020] While the present invention has been described in terms of
certain exemplary preferred embodiments, it will be readily
understood and appreciated by one of ordinary skill in the art that
it is not so limited and that many additions, deletions and
modifications to the preferred embodiments may be made within the
scope of the invention as hereinafter claimed. Accordingly, the
scope of the invention is limited only by the scope of the appended
claims.
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